The present invention relates to a novel retrovirus, a spumavirus, that has been isolated from humans. More particularly, the novel spumavirus may be used as a vector for gene therapy. The novel spumavirus may also be used as a recombinant live virus vaccine.
Spumavirus, also known as foamy virus for the characteristics of vacuolization the virus induces in cell culture, belongs to a distinct group of retroviruses. The simian foamy viruses (SFVs) include isolates from Old World and New World monkeys and are classified into 10 different serotypes based on serological cross-reactivities. Virus appears to persist in the host for a long period of time in a latent form and can exist in the presence of neutralizing antibody.
Currently the most studied retrovirus, Human Immunodeficiency Virus, is believed to be derived from nonhuman primate transmission into humans at some past time. Concerns about the risk of transmission of retroviruses from non-human primates to humans working in research laboratories were heightened in the early 1990""s when two persons developed antibodies to SIV (Simian Immunodeficiency Virus) following work-related exposures, one of whom had clear evidence of persistent viral infection. (See CDC. Anonymous survey for simian immunodeficiency virus (SIV) seropositivity in SIV laboratory researchersxe2x80x94United States, 1992. MMWR Morb Mort Wkly Rep 1992; 41: 814-5; Khabbaz R. F., et al. Brief report: infection of a laboratory worker with simian immunodeficiency virus. New Eng J Med. 1994; 330: 172-7; Khabbaz R F, et al. Simian immunodeficiency virus needlestick accident in a laboratory worker. Lancet 1992; 340: 271-3; and CDC. Guideline to prevent simian immunodeficiency virus infection in laboratory workers and animal handlers. MMWR 1988; 37:693-704.) In addition to SIV, nonhuman primate species used in biomedical research are commonly infected with SFV (simian foamy virus), STLV (simian t-cell lymphotrophic virus), and/or type D retroviruses. All of these retroviruses cause lifelong infections in nonhuman primates, and some are known to be transmissible through sexual contact, blood, or breast feeding. Natural SFV infections in non-human primates have not been definitively associated with disease. In non-human primates, infection with the other retroviruses may result in a clinical spectrum ranging from asymptomatic infection to life threatening immunodeficiency syndromes or lymphoproliferative disorders. The transmission routes of SFVs among non-human primates remain undefined, but the prevalence of seroreactivity is high among captive adult non-human primates.
Studies of the prevalence of spumavirus infection of humans are limited and the findings are not definitive. Though there is some evidence of human infection with SFV (antibodies and positive PCR results), such occurrence has been reported in only two persons, both of whom had occupational risks for infection. Associated disease was not reported in either. (See Schweizer M., et al. Absence of foamy virus DNA in Graves"" disease. AIDS Res and Human Retrov 1994; 10: 601-5; Neumann-Haefelin D, et al., Foamy viruses. Intervirology 1993; 35: 196-207; and Schweizer M, et al., Markers of foamy virus infections in monkeys, apes, and accidentally infected humans: appropriate testing fails to confirm suspected foamy virus prevalence in humans. AIDS Res and Human Retrov 1995; 11: 161-70.) There have been no published reports that virus was ever isolated from these infected individuals.
Other inconclusive evidence was seen in early studies which described a relatively high rate of seroreactivity to antibodies to spumaviruses among human populations not known to be exposed to non-human primates. In some instances seroreactivity was suggestively linked to human disease, including disorders of the central nervous system, thyroid disease, and Chronic Fatigue Syndrome. In most instances these studies lacked definitive evidence of human infection and were not subsequently confirmed. (See Heneine W, et al., Absence of evidence for human spumaretrovirus sequences in patients with Graves"" disease [letter]. J Acq Immune Defic Synd and Human Retrov. 1995; 9: 99-101; Simonsen L, et al.,. Absence of evidence for infection with the human spumaretrovirus in an outbreak of Meniere-like vertiginous illness in Wyoming, USA [letter]. Acta Oto-Laryngologica 1994; 114: 223-4; and Heneine W., et al., Lack of evidence for infection with known human and animal retroviruses in patients with chronic fatigue syndrome. Clin Infect Dis 1994; 18: S121-5).
To the knowledge of the inventors, there has not been a documented, definitive isolation of a spumavirus, such as the one of the present invention, from humans. Previous reports of human spumavirus isolates are now widely regarded as laboratory contaminants.
Recent publications indicate that earlier serological tests showing human spumavirus antibodies in the human population were incorrect. Immunological investigation of a previously reported human spumavirus revealed that it shared common antigens in complement fixation, immunofluorescence and neutralization assays with the chimpanzee foamy virus, SFV-6. Furthermore, failure to detect serological evidence of HFV infection in people from a wide geographical area suggested that this virus isolate was a variant of SFV-6, particularly since sera from chimpanzees naturally infected with SFV-6 neutralized both viruses. In a survey for prevalence of human foamy virus in more than 5000 human sera, collected from geographically diverse populations, none of the serum samples were confirmed as positive. Taken together with sequence analysis endorsing the phylogenetic closeness of the purported human spumavirus to SFV-6/7, these data strongly suggest that human foamy virus is not naturally found in the human population. (See Ali, M. et al., xe2x80x9cNo Evidence of Antibody to Human Foamy Virus in Widespread Human Populations,xe2x80x9d AIDS Research and Human Retroviruses, Vol. 12, No. 15, 1996.)
Recent concern that xenotransplantation, the use of living tissues from nonhuman species in humans for medical purposes, may introduce new infections into the human community has increased the importance of defining the ability of simian retroviruses to infect and/or cause disease in humans (See Chapman L E, et al. Xenotransplantation and xenogeneic infections. New Engl J Med 1995; 333: 1498-1501; DHHS. Docket No. 96M-0311. Draft Public Health Service (PHS) Guideline on Infectious Disease Issues in Xenotransplantation. Federal Register Vol.61, No. 185. Sep. 23, 1996.). The primary animal species considered as donors for xenografts are baboons and pigs. Thus, what is needed are compositions and methods for detecting viruses that may be transmitted from the nonhuman organ donors to the recipient human. Additionally, information regarding these transmissible agents may provide valuable information about the organ donors"" cellular receptors that may be important for transplantation success.
Gene therapies have long looked for a good vector that can transport the foreign gene of choice into human cells. The lack of any known disease associated with the virus of the present invention makes the present invention an ideal candidate for gene therapy regimens. Thus, compositions and methods for gene therapy are needed that use a vector capable of carrying a significant amount of foreign DNA that will enter the host organism and not cause disease.
Compositions and methods for vaccination using recombinant live retroviruses are also needed. A live virus, that causes no illness in humans, and that has genes of antigens of choice incorporated into its genome, would provide for an excellent vaccination tool. The retrovirus would reproduce in the human host and expose the immune system to antigens so that an immune response can be initiated.
Targeted attack on reproducing cells is a goal of cancer treatment. What is needed is are compositions and methods for cancer treatment that are specific for dividing cells that do not cause systemic damage to the cancer patient. A virus that could infect and kill dividing cells, without killing other cells of the host would provide a solution for cancer treatment.
The present invention is directed to compositions and methods comprising a novel spumavirus or foamy virus, known as SVFHu-1. The present invention comprises a spumavirus isolate of human origin that has been definitively isolated from a human with no disease. The novel spumavirus of the present invention has been maintained through tissue culture cells where it causes the characteristic vacuolation of the cells that is known for foamy viruses.
The novel spumavirus of the present invention has utility as a reagent for the immunological screening of the human population for the prevalence of such viruses in the population. The novel spumavirus of the present invention can also serve as a vector in gene therapy because the virus appears to cause no disease in humans and is not transmitted to other humans. Additionally, the novel spumavirus of the present invention can be used as a reagent in pathogenicity studies of these and related viruses. Moreover, the sequences of the novel spumavirus of the present invention can be used as probes to detect virus in biological samples. Vectors include, but are not limited to, procaryotic, eucaryotic and viral vectors. The foamy virus of the present invention can also be used as a live recombinant virus vaccine. Additionally, the spumavirus of the present invention can be used as a replicating viral system to kill live dividing cells, either in vitro or in vivo.
The spumaviruses or foamy viruses are by far the least well characterized of the retroviruses. They have been isolated as agents that cause vacuolation (xe2x80x9cfoamingxe2x80x9d) of cells in culture from a number of mammalian species, including monkeys, cattle, cats, and reportedly in humans. Persistent infection with these viruses is not associated with any known disease.
Recent studies using improved diagnostic assays have shown no evidence of foamy virus infection of humans in studies of large populations (approximately 8,000 persons). Given these results, the identification of seroreactivity in three persons occupationally exposed to non-human primates is notable. The PCR identification of viral genome sequences in biologic specimens from all three, and isolation of the virus from one, confirm virus infection in these workers.
The present invention includes the isolation and characterization of a spumavirus, SVFHu-1, that was shown to have been transmitted from non-human primates to humans at some point in the past. The spumavirus of the present invention does not appear to be readily transmitted from human to human. The spumavirus of the present invention can be used in constructing protocols for diagnosing spumavirus infections and may be used as a vector in gene therapy procedures.
The present invention also includes methods and compositions for detecting spumavirus in biological fluids. The methods and compositions, including kits, can be in any configuration well known to those of ordinary skill in the art. The present invention also includes antibodies specific for the spumavirus and antibodies that inhibit the binding of antibodies specific for the spumavirus. These antibodies can be polyclonal antibodies or monoclonal antibodies, which also includes fragments of any type of antibody. The antibodies specific for the spumavirus can be used in diagnostic kits to detect the presence and quantity of spumavirus in biological fluids or in organs from nonhuman primates for xenotransplantation. Antibodies specific for spumavirus may also be administered to a human or animal to passively immunize the human or animal against spumavirus, thereby reducing infection after accidental exposure to nonhuman primate bodily fluids.
The present invention also includes compositions and methods, including kits, for detecting the presence and quantity of antibodies that bind spumavirus in body fluids. The methods, including kits, can be in any configuration well known to those of ordinary skill in the art. Such kits for detection of spumavirus itself or detection of antibodies to the spumavirus can be used to monitor the blood supply for the presence of spumavirus in the blood supply.
The present invention also includes methods and compositions comprising recombinant live virus vaccines. The virus of the present invention has areas of its genome that make it ideal for the insertion of exogenous genes. The genes can code for any protein for which vaccination or gene therapy is desired. Because SFVHu-1 replicates at a higher level than other known foamy viruses, it is capable of providing a high level of antigen to the host carrying the virus. After administration of SFVHu-1 to the host, the virus would infect the cells, replicate and provide protein antigens to the immune system of the host. A novel aspect of such recombinant live viruses is that SFVHu-1 does not cause disease in the host organism. Additionally, there is no transmission from one host organism to other non-infected host organisms, even by close contact with exchange of bodily fluids. The recombinant live virus vaccines of the present invention are a safe way to provide antigen in a most optimum method to the immune system.
The present invention further includes methods and compositions for the use of replicating viral system to kill live dividing cells in a host or in vitro. In in vitro uses, SFVHu-1 can be used to detect and kill rapidly dividing cells. Foamy viruses, including SFVHu-1, can infect a wide variety of species of cells and can be used in many in vitro cell systems. For example, if the assay of the in vitro cell system required the identification of quiescent cells, application of SFVHu-1 to the tissue culture system would result in the selection of the rapidly dividing cells by SFVHu-1. The tissue culture cells would be infected, but because SFVHu-1 has a productive infection and cytopathic effects only in dividing cells, the dividing cells are killed by such dividing cells would be infected by SFVHu-1 and killed by such infection. The remaining non-dividing cells of the culture would remain alive.
In a host, the ability of SFVHu-1 to infect dividing cells provides an excellent treatment for conditions due to the presence of rapidly dividing cells. For example, a person with disease due to rapidly dividing cells, such as cancer or any known angiogenic condition, could be infected with SFVHu-1. Such virus may or may not carry other, exogenous genes for other effects in the host. Because SFVHu-1 does not cause disease in the host and there is no transmission of the virus to contacts with the host, only the person with the disease from rapidly dividing cells will be treated. In addition, only the rapidly dividing cells of that host person will be infected by SFVHu-1, and the rest of the body will remain uninfected. The virus will infect the rapidly dividing cells and kill them. For example, a person with a fast growing tumor would be infected with SFVHu-1 and the cells of the tumor would be destroyed by the virus. The SFVHu-1 can be recombinantly modified to be selective for cellular receptors on the tumor to make the virus even more specifically targeted to just those cells.
Such treatment with SFVHu-1 could be used for any condition in which rapidly dividing cells provide an aspect of the pathology of the condition. One such condition is the presence of uncontrolled angiogenesis within the body. Angiogenesis dependent diseases are well known in the art and are caused in part by the rapid growth of blood vessels.
Accordingly, it is an object of the present invention to provide a composition comprising a novel spumavirus.
It is another object of the present invention to provide a method of detecting a spumavirus.
It is yet another object of the present invention to provide methods and compositions for detecting the presence and amount of spumavirus in a body fluid or organ.
A further object of the present invention is to provide compositions and methods for treating genetic and physiologic disorders using gene therapy techniques comprising the novel spumavirus of the present invention as a vector for nucleic acid sequences and antisense sequences.
Another object of the present invention is to provide compositions and methods useful for manipulating the expression of genes.
Yet another object of the invention is to provide vaccines.
Yet another object of the present invention is to provide compositions and methods for treating viral infections in humans or animals.
Another object of the present invention is to provide compositions and methods that are effective in treating genetic diseases.
Yet another object of the present invention is to provide a method of treating microbial infections in humans or animals.
It is another object of the present invention to provide for treatments of conditions that are caused in part by rapidly dividing cellular growth.
Another object of the present invention is to provide live recombinant virus vaccines.
An object of the present invention is to provide diagnostic tools such as antibodies or antigens for the monitoring of the blood supply or organ and tissue donation for the presence of spumavirus.
These and other features and advantages of the present invention will become apparent after a review of the following detailed description of the disclosed embodiments and the appended claims.